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CAIE A-Level Chemistry AS 5.1.4 Energy Transfers Occur During Chemical Questions

Practise explaining energy transfer between a reacting system and surroundings during exothermic and endothermic reactions using CAIE 9701 AS questions.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • Explain that energy transfers occur during chemical reactions and relate them to exothermic or endothermic changes.

CAIE A-Level Chemistry AS 5.1.4 Energy Transfers Occur During Chemical Questions question 1

[Maximum number: 1]

At 550∘C550^{\circ} \mathrm{C} nitrogen dioxide reacts with unburnt hydrocarbon fragments, such as CH3\mathrm{CH}_{3}, in the catalytic converter of a motor vehicle.

4CH3+7NO2→312 N2+4CO2+6H2O4 \mathrm{CH}_{3}+7 \mathrm{NO}_{2} \rightarrow 3 \frac{1}{2} \mathrm{~N}_{2}+4 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O}

Which row gives the energy change for this reaction and a possible reason for it?

energy change of reaction

reason why the reaction is endothermic or exothermic

endothermic

chemical energy is converted to heat energy

endothermic

the N≡N\mathrm{N} \equiv \mathrm{N} bond energy is very high

exothermic

CO2\mathrm{CO}_{2} and H2O\mathrm{H}_{2} \mathrm{O} have negative ΔHf⊖\Delta H_{\mathrm{f}}^{\ominus} values

exothermic

double bonds are broken in NO2\mathrm{NO}_{2}

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